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Old Apr 27, 2009, 1:17 PM   #1
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I'm wondering if there are any specs (at least advertised or proven) to let us know how fast a lens will focus.

The reason I ask is that I notice an incredible difference in focusing speed between two of my lenses. My camera is a D40. The 18-55 kit lens focuses so slow it's pathetic. My 55-200VR is super fast. Obviously the 18-55 kit lens is a faily cheap (but very good given it's cost) lens so maybe that is a compromise in it's focusing motor.

Why the difference and how can I judge future purchases without actually trying them? I want it fast!
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Old Apr 27, 2009, 2:07 PM   #2
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On average, most consumer grade lenses (such as the ones you mention) will be slower to focus than the mid grade/pro grade lenses that have large/constant minimum apertures (2.8). However, focus speed is also dependent on the scene you are shooting. Lower light, low contrast scenes will cause the af to focus slower as well. Also, the D40 being an entry level camera will have slower focusing as well. For the most part, in average light, even with consumer lenses on a consumer body, your focus speed should still be pretty snappy.

If you want really fast, you'll need a prosumer/pro body, with good glass, which is quit expensive.
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Old Apr 27, 2009, 2:21 PM   #3
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This is interesting



I have the AF-S 18-55mm, 3.5-5.6 GII ED I believe this would be the same as your lens. It focuses quite fast on my D50. Much faster than my Sigma 28-200mm



The D50 has a built in focus motor which the D40 does not, but it is not used with the AF-S lenses.



It is possible you got a bad lens. You might want to check that out and have the lens replaced or repaired under warranty.


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Old Apr 27, 2009, 6:59 PM   #4
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How does Nikon distinguish between their consumer & pro lenses?

They don't seem to be different categories on the website but they do vary considerably in price.
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Old Apr 27, 2009, 7:00 PM   #5
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Still wondering if there are any specs available for lenses such as "time to focus over entire range" or anything like that.
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Old Apr 28, 2009, 2:28 PM   #6
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mckeand13 wrote:
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Still wondering if there are any specs available for lenses such as "time to focus over entire range" or anything like that.
Price is a good determination. More expensive lenses with large minimum aperatures will typically focus faster. It's impossible to set specs, as the lenses will perform differently on different bodies and in different conditions. As I said before, your focus speed in low light will be much different than in bright light. Low contrast scenes will also result in slower focusing, or very busy scenes where it's difficult to lock onto a subject will slow things down as well.

So look for very expensive lenses, or lenses that are f2.8 or better first. Also Nikons AF-S lenses tend to be quicker, sigma uses an HSM designation.

Again, your d40 (as well as the D40x, D60 and D5000) will tend to be slower because of the lack of focus motor in the body.






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Old Apr 28, 2009, 9:19 PM   #7
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Quote:
Again, your d40 (as well as the D40x, D60 and D5000) will tend to be slower because of the lack of focus motor in the body.


I wonder about this. If an AF-S lens is used on .. say.. A D300 will it focus any slower than an older AF (not AF-S) lens?



Remember the cameras motor is not used with the AF-S lenses, even if its there. As far as I can tell not even the biggest, heaviest AF-S lenses have the needed screw. (Someone correct me there if I'm wrong).



Nikons lens line is slowly but surely making the switch to AF-S lenses. Surely they would not be doing this if these lenses were slower.



Granted the AF systems in the lower end cameras are going to be slower than in the higher end cameras. But is the motor being in the lens rather than the camera the issue? Are these lenses inferior?
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Old Apr 29, 2009, 8:35 AM   #8
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tjsnaps wrote:
Quote:
Quote:
Again, your d40 (as well as the D40x, D60 and D5000) will tend to be slower because of the lack of focus motor in the body.


I wonder about this. If an AF-S lens is used on .. say.. A D300 will it focus any slower than an older AF (not AF-S) lens?



Remember the cameras motor is not used with the AF-S lenses, even if its there. As far as I can tell not even the biggest, heaviest AF-S lenses have the needed screw. (Someone correct me there if I'm wrong).



Nikons lens line is slowly but surely making the switch to AF-S lenses. Surely they would not be doing this if these lenses were slower.



Granted the AF systems in the lower end cameras are going to be slower than in the higher end cameras. But is the motor being in the lens rather than the camera the issue? Are these lenses inferior?
All my lenses are noticeably quicker on my D300, AF-S included, than on my d80.
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